RESUMO
Actin plays a critical role in the rhizobium-legume symbiosis. Cytoskeletal rearrangements and changes in actin occur in response to Nod factors secreted by rhizobia during symbiotic interactions with legumes. These cytoskeletal rearrangements are mediated by diverse actin-binding proteins, such as actin depolymerization factors (ADFs). We examined the function of an ADF in the Phaseolus vulgaris-rhizobia symbiotic interaction (PvADFE). PvADFE was preferentially expressed in rhizobia-inoculated roots and nodules. PvADFE promoter activity was associated with root hairs harbouring growing infection threads, cortical cell divisions beneath root hairs, and vascular bundles in mature nodules. Silencing of PvADFE using RNA interference increased the number of infection threads in the transgenic roots, resulting in increased nodule number, nitrogen fixation activity, and average nodule diameter. Conversely, overexpression of PvADFE reduced the nodule number, nitrogen fixation activity, average nodule diameter, as well as NODULE INCEPTION (NIN) and EARLY NODULIN2 (ENOD2) transcript accumulation. Hence, changes in ADFE transcript levels affect rhizobial infection and nodulation, suggesting that ADFE is fine-tuning these processes.
Assuntos
Fatores de Despolimerização de Actina/metabolismo , Phaseolus/metabolismo , Proteínas de Plantas/metabolismo , Rhizobium/metabolismo , Fatores de Despolimerização de Actina/genética , Fixação de Nitrogênio , Phaseolus/genética , Phaseolus/microbiologia , Proteínas de Plantas/genética , Rhizobium/genéticaRESUMO
Mammalian sperm require to undergo an exocytotic process called acrosomal exocytosis in order to be able to fuse with the oocyte. This ability is acquired during the course of sperm capacitation. This review is focused on one aspect related to this acquisition: the role of the actin cytoskeleton. Evidence from different laboratories indicates that actin polymerization occurs during capacitation, and the detection of several actin-related proteins suggests that the cytoskeleton is involved in important sperm functions. In other mammalian cells, the cortical actin network acts as a dominant negative clamp which blocks constitutive exocytosis but, at the same time, is necessary to prepare the cell to undergo regulated exocytosis. Thus, F-actin stabilizes structures generated by exocytosis and supports the physiological progression of this process. Is this also the case in mammalian sperm? This review summarizes what is currently known about actin and its related proteins in the male gamete, with particular emphasis on their role in acrosomal exocytosis.
Assuntos
Reação Acrossômica/genética , Acrossomo/metabolismo , Citoesqueleto de Actina/genética , Actinas/genética , Exocitose/genética , Capacitação Espermática/genética , Acrossomo/química , Citoesqueleto de Actina/química , Citoesqueleto de Actina/metabolismo , Fatores de Despolimerização de Actina/genética , Fatores de Despolimerização de Actina/metabolismo , Actinas/química , Actinas/metabolismo , Animais , Proteínas Quinases Dependentes de AMP Cíclico/genética , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Regulação da Expressão Gênica , Humanos , Quinases Lim/genética , Quinases Lim/metabolismo , Masculino , Camundongos , Fosfolipase D/genética , Fosfolipase D/metabolismo , Proteína Quinase C/genética , Proteína Quinase C/metabolismo , Transdução de SinaisRESUMO
Actin depolymerizing factors (ADFs) have been recently implicated in plant defense against pathogenic fungi, associated with the cytoskeletal rearrangements that contribute to establish an effective barrier against fungal ingress. In this work, we identified a DNA fragment corresponding to a part of a gene predicted to encode an ADF-like protein in genotypes of Fragaria ananassa resistant to the fungus Colletotrichum acutatum. Bulked segregant analysis combined with AFLP was used to identify polymorphisms linked to resistance in hybrids derived from the cross between the resistant cultivar 'Sweet Charlie' and the susceptible cultivar 'Pájaro'. The sequence of one out of three polymorphic bands detected showed significant BLASTX hits to ADF proteins from other plants. Two possible exons were identified and bioinformatic analysis revealed the presence of the ADF homology domain with two actin-binding sites, an N-terminal phosphorylation site, and a nuclear localization signal. In addition to its possible application in strawberry breeding programs, these finding may contribute to investigate the role of ADFs in plant resistance against fungi.